Hydraulic transmission



May 14, 1935. c.. E. lvEs HYDRAULIC TRANSMISSION M @uw May 14, 1935. c. E.v lvEs HYDRAULIC TRANSMISSION 6 Sheets-She'at 3 K cw, k

Filed April 9, 1932 NNN i @VH wif/A14 iw Tw 6 Sheets-Sheet 4 c. E. NES

HYDRAULIC TRANSMISSION F-led April 9, 1932 May 14, 1935.

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May 14, 1935. I C E. lvEs v 2,001,325

HYDRAULG TRANSMISSION Filed April 9, 1932 6 Sheets-Sheet 5 juve/@071' r Clifford Elves ZZUS,

May 14, 1935. c. E. lvEs HYDRAULICITRANSMISSION Filed April 9, 1952 l6 sheets-sheet 6 QQ NS MQ bx IweIzZOr.' CZzfford E. Ive

r ZZJS Patented May l14, 193s Unirse srArss PATENT ori-ica 43 Qlaims.

My invention relates in general'to e:variable on an automobile for transmitting the movement of the automobile engine crank shaft to the propeller shaft.

In automobile development work, particularly in the portion thereof that relates to the transmission of power from the engine to the wheels, there has been a gradual tendency in several directions, all more or less having to do with-automatic clutch control, automatic gear shift control, free-wheeling and the like. One of the developments looked to to produce improved operating characteristics along the lines suggested is in the use of hydraulic transmission mechanisms.

It has been understood for some 4considerable length of time that, with a hydraulic drive properly controlled, it might be possiblevt'o do away with the ordinary friction plate clutch entirely.

Consequently, there hasbeen intensive development and experimentation along this line, as well as along other lines, to produce limproved driving and transmission characteristics in automobiler..

Heretofore so-called hydraulic transmission mechanisms have notbeen 'satisfactoryrj/The i y principles employed have made it impossible to secure the simple and direct control, theoretically possible in a hydraulic transmission, without at the same time introducingproblems in oil heat,- ing, oil leakage, and the like. Moreover, very often instead i simplifying the control of an automobile, thefproposed hydraulic transmission has so complicated the work of the driver as to make it impossible, or at least impractical, to place the hydraulic transmission on automobiles intended for operation by the rank and file of drivers. Care and upkeep of standard types of mechanical transmissions and clutches have become so simple that very little, if any, attention need be given to these devices by ordinary drivers. Moreover, the devices, with only ordinary attention, will usually last the life of the automobile. No hydraulic transmission is of any practical 'valueunless it can be employed with no more care than now expended `-on the corresponding mechanicalv transmissiomand unless it is capable of lasting practically the life of the car with only ordinary care. J

Exceedingly high torque hydraulic drives, and this complicates the actual use oi the hydraulic transmission when placed in ratios are possible with (ci. sei-19) the hands of the ordinary driver. unless a practical safety means is provided for avoiding injury to the mechanical portions of the mechanism entering into the drive. l

The principal object of the present invention is to transmit power hydraulically at variable speedsfrom the engine crank shaft to the driving shaft in such a way as to avoid all of the diilculties hereinabove outlined.

Another object is the provision of a lwdraulic 10 transmission adapted for use under all conditions without the employment of a separate clutch in the drive train. .V l

`Another object is the provision of a hydraulic transmission capable of operating en a so-called 15 free-wheeling principle, or in such a way as to use the engine as a brake.

Another object is to obtain greater braking efficiency vfrom the engine than has been possible heretofore.- Y

Another object is the provision of a hydraulic transmission in which the drive is uni-directional from the engine to the propeller shaft, but which y may be adjusted to provide a bi-directional drive.

Another object is the provision of a hydraulic 25 transmission which can be made to operate sube stantiallyindeflnitely withoutchanging the hydraulic` fluid.

Another object is the provision of a hydraulic transmission of high eiilciency, in which. sumitari- 30 .tially all. of the power input is transmitted to the driven shaft' whereby there is a, minimum loss of power manifesting itself in heating of the oil.

Another object is the provision of a hydraulic transmission operable in a full range of speeds 35 from substantially infinite gearratio to an overdrive ratio, if desired.

Another object is the provision of a transmission mechanism in which the reverse drive includes a continuous range of speeds from sub- 40 stantially infinite gear ratio to the maximum l speed ratio determined by the limits of the design.

transmission operable by a single control lever having a neutral position and operating in one direction to control the range of speeds forward 5o from neutral to full forward drive and operating in the opposite direction to produce a full range of reverse speeds from 'neutral to full reverse drive.

Another object isthe provision of a hydraulic 55` transmission operable to produce "free-wheeling and in which the driver can shift from free-wheeling to conventional direct drive or back at any time. p

Another object is the provision of a hydraulic transmission device having a relatively wide neutral zone between the forward and reverse drive positions.

Another object is the provision of a hydraulic transmission having a-.complete range of spee l in both forward and reverse.' Another object is the provision of a hydraulic vtransmission Vhaving safety means for preventing the application of too great a load upon the mechanicall portions of the automobile.

' Another object is the provision of improved means in a hydraulic transmission for removing air and/or other foreign matter from the hydraulic fluid. A

Another object is the provision of improved means in a hydraulic transmission for maintaining the hydraulic fluid\at a' relatively low temperature. l

Another object is the provision of a hydraulic transmission provided with automatic means -for 'decreasing the torque ratio and changing the relative speed of rotation between the crank Ashaft and the propeller shaft.

Another object is to control the rate at which the automatic speed change takes place, whereby the gear ratio may be brought up to direct drive at any pre-determined `automobile speed.

Another object is the provision of a hydraulic 'transmission mechanism operated on the freewheeling principle, but adapted to 'form a bidirectional drive when the automobile brake is applied, whereby the engine functions asa brake during the braking of the car.

Another object is the provision of a hydraulic transmission wherein there is substantially no oil movement in direct drive.

Another object `is the provision of a hydraulic.

transmission adapted to change the drive ratio in accordancevwith the cars speed when operating in both forward and reverse directions.

Anotherf object is the provisionof a hydraulic ltransmission and means for changing the drive ratio thereof automatically in both forward and reverse.

Other objects and features of the invention will be apparent from, a consideration of the following detailed description taken with the accompanyingv drawings, wherein Fig. 1 is a longitudinal, somewhat irregularf 'along the same line as Fig. 2, but looking in the opposite direction;

"tion ofone of the oil ports;

- Fig. 5 is an irregular'transverse sectional view taken along the line -'of Fig.' 1;

Fig. 6 ispa fragmentary' sectional view taken-A on the line 56--6 of Fig. 4, and showing the loca.-

Figs.' 'l/l to 10, inclusive, are diagrammatical illustrations of the hydraulic principle employed in .uw transmission device); f

l Fig. 1 1 is a mathematical chart showing torque ratios for various positions of the control means in both forward and reverse;

Figs.- 12; 13l and 14 are somewhat diagrammatical views of the reverse, neutral and forward positions, respectively, of the ported means of control;

Fig. l5 is. a hydraulic flow diagram of the system; i 1

Fig.. 16. is a fragmentary cross section taken alongxthe line Iii-I6 of-Fig. 1;

Fig.' 17 is a fragmentary sectional view taken along the lineA I'l-Il of Fig. 4;

Fig. 18 is an elevational view showing -the cooling and air separating tank, the free-wheeling control and some of thepipe connections; and

Fig. 19is an elevational view showing features of the device, including modications in the control therefor. Y In carrying out my invention, I employ a variable capacity pump operated by the power input shaft and a x'ed capacity pump controlled by the fluid suppliedI to it by the variable capacity pump. In its simplest form, the fixed capacity pump is of the rotary vane type. having a vane rotor driven directly bythe power input shaft kand an outer casing connected directly to the power output shaft. Control of the power output shaft is accomplished by varying the capacity of the variable capacityy pump. When the capacity of the variable pump is adjusted to' the same capacity as the fixed pump, the rotor of the xed capacity pump revolves within its casing at the same relative speed with respect to the casing as the input shaft speed. In other words, the two rotors driven togetherl have the same speed with respect to their respective casings, with the result.that the power ouput shaft connected directly to the casing of the xedcapaccomitantly to the power output shaft connected to it. It will be understood that by the terms fixed capacity pump and variable 'capacity pump I mean the capacity per revolution, and

the capacity per revolution is determined not by the speed of the rotor but by the relative speed in each instance lbetween the rotor and casing. The variable capacity pump casing is stationary in the present embodiment of the invention and so-its capacity per unit of time is determined directly by the number of revolutions of the rotor. 'I'he fixed capacity pump, however, having a rotatably mounted casing, hasv a fixed capacity per kWhen the variable capacity pump is set to zero capacity, the casing ofthe xed capacity pump will turn substantially directly with its rotor, so thatfat direct drive the rotor and casing of the fixed capacity pump rotate as a unit and there is subs ntially no movement of hydraulic fluid therethrough. Conversely, when the capacity \per revolution of the. variablecapacity pump is set greater than the `capacity per revolution of the fixed capacity pumpfthere will be a necessary greater relative speed between the rotor :and casing or stator o! the fixed capacity pump.

l is forced to move in a reverse direction and the the description progresses.

Vmovement of the output shaft is concomitantly in a reverse'direction. l

This is briefly the principle around which my present transmission mechanisnis developed. In its present form, as hereinabove indicated, it employs a rotary type of pump.v When the hydraulic principle employed is understood, however, it will be obvious that-the principles may be embodied in any design capable of accomplishing the necessary movement of the hydraulic uid, and of stabilizing or arresting the movement for the purpose outlined. I prefer, however, the rotary type of pump, such as shown, for reasons whichV will appear obvious. For a more fundamental understanding of the principles involved, I shall refer briefly to Figs. 7 to 10 inclusive.

Each of Figs. '7 to 10, includes a flxedcylinder 2| and a floating cylinder 22, for convenience the cylinders 2| being differentiated from each other by letters a, b and c, the cylinder 2| being small and increasing in diameter at 2|a, '2|bl therefore, R=2P. Translated'. into terms of and 2|c, respectively; The cylinders 22 are all of-'the same size and same capacity. A piston rod 23 extends through each pair of cylinders 2| and 22. In-each of the'cylinders 22, a piston A is operably attached tothe rod 23. The cylinder 2| has no piston, while each of the cylinders 2|a to 2 Ic is provided with a piston a secured to the rod and operable therewith. that ,the cylinder 2| has the same inside diameter as the rod 23, so that the capacity thereof is zero. For the purpose of explaining the principles here employed, however, I am assuming a piston a: also disposed in the cylinder 2| of 'zero capacity; in other words, this piston has the same diameter as the rod 23.`

For the purposes of analogmthe rod `23 corresponds tov the input shaft of my transmission and an extension 2B corresponds to the output shaft. The pistons a and A correspond to the rotorsI connected directly to the input shaft. The cylinders 2| to 2|c, inclusive, correspond to the non-rotatable or fixed stator, and the cylinder 22 corresponds to the rotatably or movably mounted stator of the fixed capacity pump connected directly to the. power output shaft of the transmission. The ends of the cylinders 2| and22 are connected by exible pipes indicated bythe dotted lines 26V and 21, these connections being equivalent, for `purposes of analogy, to the connections between the two pumps which I employ, as will be made clearas For the purpose of analyzing the hydraulic principle involved, I assume the application of a pressure P on the rod 23, and the eiect `of this pressure is measured on the extension 24, and the value thereof indicated by the character R. .It will at once be obvious that I am ex`- plaining Figs. I to l0 in terms of pressure and resistance to pressure. This is done rorthe purpose of simplicity, it beingunderstood, of course, that P and R could be measured in terms of linear movement.

Now assume the application of a pressure P Vtute in our formula It will be seen 4 en the red-'23 in Fig. v in the direction indicated l by the arrow. The cylinder 2| is of zero-dise I placement and it is impossible for oil to pass in either direction throughfeither the pipe 28 -or the pipe 21. Thepiston A cannot move within the movably supported cylinder 22, and' sogthel pressure applied at P on the rod 23 is trans'- .mitted directly. to the'member 24. It` follows,

also, ofcourse, that whatever Amovement is' imparted to the rd' z3 is else imparted direeuy to the movable cylinder 22 and the extension 24. This corresponds to direct forward drive. -f

. The value of R is very easily determined. by means of a simple algebraic equation,

Supplying the value of 'a in the equation, (applying zero value to a as in Fig. 7) we have than the capacity of the cylinder 22 and a has a smaller areathan A. Assume an area of the two pistons of the order of 2 to l. We substi- In Fig. .9, the pistons a and A are the sme size, so that, in accordance with the legend at the left of the figure, movementof the rod' 2 3 will not produce any movement of the extension 2t for the reason that when oil ahead of the pislton- A is displaced, it ows to` the cylinder 2lb behind the piston a, and the oil ahead of piston a and displaced by it flows over to llup the -space behind the piston A. In other words, since the displacement of the two cylinders or pumps is the same, the shaft 23 can be'moved in either direction without any movement of the floating cylinder 22. Therefore, there is a. theoretical innite pressure ratio equivalent -to an infinite torqueratio between an input and output shaft. In Fig. l0, the cylinder 2|c is larger than the cylinder 22. Applying the formula, we lnd-that R has a minus value, or, in other words, the

movement of the cylinder -22 is always in a reverse direction to the movement of the rod 28.

The rate of reverse movement is determined entirely by how much the area of piston a is greater than the areaof piston A.

From a discussion ofv these four figures, `it is clear that if means are providedfor varying the capacity .of the piston a, any drive characteristic desired may beobtained. In the practical carrying .out of my invention, this' is the result which I obtain.v I shall now refer to the mechanical structure with which my principle is clothed in the present embodiment.

Referring now to Fig. l, and the sections taken thereon,.I employ an input shaft 3| projectinginto a casing 32, and an output shaft 33 adapted by hydraulic means, to be described, to receive motion from the shaft 3|. The shaft 3| carries Y vit shaft 3| may be made effective to drive ,the shaft.-V

33 at any range of speeds from zero to direct drive and also in reverse at any gear ratio or torque .rati possible within the limits of a particular design.

Now, consider the construction of the variable capacity pump itself shownparticularly in Figs. 1 and 3. The rotor 34 includes a. vane block slotted to receive vanes 4|. The vane block is secured to the shaft 3|. by keys 42 and the inside of the block is provided with a pressure space 43 adapted to carry hydraulic-fluid under pressure to assist in holding the vanes downwardly against the stator block 36. These vanes also tend to move out under centrifugal force when the shaft 3| isturning. v

In 4a pump of this character,` several different means for varying the capacity may be provided.

I I employ a control plate 44 provided with a plurality of ports, which will be identified and describedmore in detail hereinafter, for delivering oil to the pump and receiving the discharge therefrom. 'As will be seen by a consideration of Fig. 3, the pump is provided with four quadrants, so that in reality it comprises four pumps in one,

, with four intakes and four outlets. The control plate 44 forms one side of the casing, while a plate the port. housing 41 and the other side abutting the stator block 36. The spacer 49 has the function of providing the needed space for the aclinstable control plate 44, so that when a main housing cover 5| is bolted to the housing, all of the stationary/'parts maybe drawn up tightly without wedging the control plate in so as to prewish topoint outthat in a transmission unit of this character, it is desirable to. fit everything ,relatively snugly so. as to prevent leaks. It is well understood that oil passing through leaks means a loss of power resulting in the generation of heat which, if sufficiently high, may cause a failure.

Now 'conslderingrthe fixed capacity pump, as

appearing more in detail in Fig. 5, this is of the same general character as the variable capacity pump, including vanes 52 disposed in substantially radial slots in theV rotor block 31, the rotor block being'provided with an internal opening 53 communicating with the inside edges of the vanes so .that oil under pressure is available for assisting and holding the vanes in 'projected position. The means for supplying fiuid to the opening 53 and the open' spacel 43 in the yvariable capacity pump will be treated of hereinafter.

The fixed capacity pump is provided with a lstator block shaped to provide with the rotor a four quadrant pump similar to the variable capacity pump. To complete the stator housing, Ij

provide'ahousing plate 53 one side of which is flnishedto provide .a surface against which the `rotor-31 operates, backed by a plate 51, which is either integral with or connected to the 'output shaft 33. vAt the opposite side of the stator block, is aff-rotatable ported plate 54 and a rotatable porthousing 58 (which for convenience hereinafter will bereferred to as the rotatable port housing), and the stator, including the stator block, end plates and' rotatable port housing, is' secured in 'assembled relation by nuts and bolts 59.

. Referring to Fig. 1 more in detail now, itv is seen that I have a variable capacity pump, the capacity of which is adjusted by the control plate 44; an outer stationary port housing 41; an inner rotatable port housing 58. carried by the stator of a fixed capacity pump, the rotor 0f which is in the preceding sentence, I varyethe capacity of the variable capacity pump and bysuch means control the movement of the stator of the xed capacity pump, which, in this instance, is analogous to the,cyllnder 22 of Figs. '7 to9. 'I'he control plate 44 is adjustable to change the capacity of the variable capacity pump. The stationary. port housing 41 is constructed to receive the output from the variable capacity pump and the 'rotatable port housing is so disposed with relation to the stationary port housing as to receive the hydraulic fluid therefrom land supply it to the fixed capacity pump. Concomitantly, the fixed and rotataable porthousings are also constructed to Ireturn the hydraulic fluid from the fixed capacity pump to the variable capacity pump.- In other words, theseport housings are analogous from one standpoint to the pipes 2,8 and 21 shown schematically in Figs. 7 to 9.N

Considering the stationary port housing 41 now more in detail, it isV provided with a plurality of ports 6| for receiving oil from the variable za-'-` pacity pump in other words, theseports are connected'to -outlet ports in the control plate 44, as will be described. The ports 8| communicate with an annular distributor ring or opening 62 in the stationary port housing 41, so that, in a vent movement thereof. In this connection, I.

manner to be described, oil may be distrib d with a. plurality of ports 63 which are the return ports for delivering oilhdischarged by the fixed capacity pump tothe intake side of theovariable capacity pump. These portscommunicate with the ported control plate 44 and also communiv cate with anannulardistributor ring or opening .64 in the stationaryport housing 41.

Now, considering the rotatable port housing 58, it isprovided with a pluralityof ports 66, comlmunicating at one end by an offset with the'intake side of the fixed capacity pump and at the other end with the annular distributor 62, inthe' stationary port housing 41. The rotatable port housing Il also -provided with ports 61 (Figs. l

and 4) communicating with the outlet'or exhaust side of the fixed capacity pump andv also with l the annular distributor 64 inf' the stationary port housing 41.

Each of the sets of ports in the embodiment shown is provided in multiples of four, this arrangement working out satisfactorily with a four quadrant pump of the character shown. vWe have'then eight ported openings in both the stationary port housing and in the rotatable port housing, with a pair of distributor rings or annular passageways for connecting these sets of ports together, so that the oil delivered from the variable capacity pump always has a free port openingto the fixed capacity pump and the oil from the fixed capacity pump always has a direct passage to the variable capacity pump. This statement is true insofar as th-e ports themselves are concerned. .The actual flow of oil, however, is modified in diierent ways. and for various reasons, principally by the control of the ported control plate 44. y

This ported control plate is shown in Figs. 1, 2 and 3. The ported control plate is provided with alternate intake ports 68 and exhaust ports'69. On the side of the control plate, adjacent the stationary port housing lil, these ports are shaped as shown in full lines in Fig. 2; but these ports as they extendthrough the plate are shaped to communicate with the respective intake and outlet ports 63 and Si respectively in the stationary port housing 4l. The ported control is normally stationary, but it may be partially rotated on the shaft for control purposes. For adjusting the position of the control plate, I employ a recipro-` cable rack H supported in the casing and provided with teeth 12 meshing with teeth I3 on the periphery of the control plate. 'I'his rack has a suitable connection, as shown, with a shifting lever whereby pivotal movement of the shifting lever is eiectiveA to move the rack 'H vertically andpcause a corresponding rotational movement of the control plate dit.

As shown in Fig. 2, the control plate is in neul trai position, that is, it is set so that the capacity of the variable capacity pump is the same as the capacity of the fixed capacity pump. This is a position corresponding to the schematic Fig. 9 and' at this position there would be no movement of the output shaft 33. Pulling the control lever backwardly or in a left-hand direction (looking at Fig. l) will raise the rack 1l, thereby rotating the controlplate in a clock-wiseq direction (looking at Fig. 2) and decreasing the capacity of thel pump.

l This decrease in capacity is best understood by studying Fig. 3. In this figure, the control plate .44 containing the intake ports 68 and the rexhaust, ports 69 is shown in back of the rotor which carries the vanes di.

At the position of the control platein this figure, the pump has a capacity approximately 20% lessthan its maximum, or about the same capacity as the fixed capacltypump, (assuming a maximum capacity of 2.5% greater than the xed capacity pump). 'The space between the vanes is substantially exactly equal to the space between the ports. As` a result, when the intake port is closing the exhaust port is at that instance opening to the space between any set of vanes.

When the vanes are moving outwardly to the pcint of Amaximum rise, there is a constant suction due to the volume in the space enclosed by the vanes and stator wall progressively growing larger. If this space is in communication with oil to and fromy the variable capacity pump in a an intake port during the entire suction period, then we have a condition in which the pump dclivers its maximum capacity. With the ports set asin Fig. 3, however, the intake port is closed and the exhaust portA opened for a very short time (4 radially, approximately), andso instead of withdrawing all of tire oil from the intake port, .some oil is withdrawn from the exhaust port. As soon as the rear vane of any pair of vanes reaches the rise,or pressure side of the quadrant, however, discharge begins to take place, and the oil is delivered to the exhaust portl 69.

It should be remembered that since there are anumber of ports, a multiple pump of this character is dischargingoil at all times when set to deliver oil. Even though there are times when some oil is drawn in through an exhaust port, there is a relatively large amount of oil being delivered through another exhaust port to compensate for it and the iinal result is a steady stream of oil substantially without pulsation. The uneven number of 'vanes aids in obtaining this result. A

As the control plate 45 is moved in a counterclockwise direction in Fig. 3, ,there is gradual-,-Y ly more oil drawn from the outlet ports and less from the inlet ports, until, in apposition of zero capacity, the ports overlap the intake. and outlet positions of the stator, and the oil is merely moved back and forth through the ports, both intake and exhaust ports being exactlypsimilar in this respect. The position of the ports at zero capacity is best understood by considering that if a radial line/'were `drawn between the intake and exhaust portions of a pump quadrant, such 'v line would divide one of the ports into two exactly equal ports. a -r If the ported control plate is moved to a position beyond that described in the condition of zero capacity (direct forward drive) there is gradually more oil drawn from the exhaustuports $9 than from the intake ports SQ, which results in a reversal .of the ports and a flow oi reverse direction. By this provision, overdrive is obtained. n a

In the embodiment shown, particularly as will vbe explained in connection with Fig. 11, the varior the shaft 33 will turn at one-fourth the speed `cc of shaft 3i and in a reverse direction.

As to further detalls oi the control mechanism, I provide a spring pressed detent 16 engaging in a cam slot in the. rack to hold the rack in the neutral position in which it is A fiat spot 11 is adapted to engage against the lower portion of the rackto limit the upward movement thereof inull forward position while a corresponding iiat spot 18 iunctionsas a stop by engaging againstthe rack in its lowermost or 7,0

full reverse position. As the drawings show,r there is nothing to prevent` the controls from being held in any intermediate position. -Inother words, aiull range of speeds is available witir no iimitationrequiring a nxed drive or 75' 5 vanes of the two rotors for the purpose of aiding tion of the stator has been termed. Looking at them in maintaining their position against the stator casing or stator block, as the annular pr- Fig. '1, I provide a separate chamber 98 in the stationary port housing, closed at one end by a screw plug 99, and closed at the opposite end by Athe control plate 40. -The annular distributor 62 is in communication with this chamber by a port I 0i in a shell |02 disposed in the chamber'. The chamber is also in communication with the annular distributor ,04 through a port' |03, this port being disposed between one of the return ports 63 and the chamber 98V. A valveor piston |04, slidablv disposed within the chamber, is adapted to seat in one direction against the shell |02 and in the other direction against lau annular shoulder |06 provided in the chamber. 1

Immediately edjeeent the chamber sa is e high pr chamber |01 (seeFig. 4), in communication with theI chamber 98 by a port-|08. In the Y operationof the transmission, high pressure may be present in either the port system running from the variable capacity -pump to the'xed capacity pump (which may be termed the supply circuit) or i'rom the port system leading from the iixei capacity pump to .the variable capacity pump e the ports |0|7or |02 high pressure may be in communication with -either side of lthe"valve chamber 90. As a result, the valve or piston |04 is always forced in a direction lto close the ldw pressure side. thereby always maintaining a direct hydraulic connection between the port |08 andthe high pressure side of the system.

Since by this means relatively high hydraulic pressure is maintained in the high pressure chamber m1 during substentiem the entire time that the transmissionis in operation, any1 ported means for admitting pressure from the high pressure chamber to the vanes will accomplish mygresult. I show an annular port |09 formed partLv inthestationary port housing 41 and partly in the ported control plate 4d. This annular chamber is in communication with the pressure chamber |01 by a port which can be seen in.

Fig. l in dotted lines running at an angle andthen vertically to connect the two chambers. communicating port |f|| is also shown in Fig. 16. l

Referring now to Fig. 3, a plurality of slots H2 disposed midway between the keyways 42 are provided in the rotor block and communicate with, the annular port |09 on one side `by in full lines suitable meansshown and on the other side with the pressure space 43 directly'communicating qwith the inner edges of the vanes 4i To communicate hydraulic pressure to the vanes in thefixed capacity pump, I provide a hol-- low space H3 in the shaft 3| with which the pres-, Sure space 43 is in communication by a radial.

.port H0. At the xed capacity pump, 'radial ports H5 communicate with the .pressure space 83 in the rotor bleek, which space, as in the case of the variable capacity pump, is also in communication with the associated rotor vanes.

I also^provide safety meansfor limiting the pressure which can be developedin the pressure l' side ofthe system. There is always a pdssibility of breakage, particularly when running at com.-l paratively low speed` or when the torque ratioiis i return circuit). In other'words, through- This -to provide a valve seat H0, against which a valve |2| is adapted to seat. This valve is normally pressed against the seat by a spring |22, the

pressure of which may be regulated by ya pressure nut |23 screwed into a boss |24 in the main casing s2. is adapted te be closed by a plug |26. By this means,'it is clear'that the spring |22 may be set tbanysuitable` prede-v termind pressure, so -thatw when pressure in either side of the-system in communication with the chamber 08 through the action of the valve |04 is raised to a point which will taxl the me chanicalstrength of any of the/associated apparatus, the valve |2| will be opened and soine-of the oil will be vented into the low pressure chaml' ber 84 in thecasing. l

To avoid building up `a high end thrust between the. various-portions of the transmission, 1 vent to atmosphere any portions thereof in which the high pressure communicating to space which may be found between the parts would cause ran end thrust against such parts.Y For example, between the rotatablev porthou'sing 50 andthe stationary block 65, I provide. an annular space |21 connected by one or more vents |28 (Fig. 16) with the low pressure portion of the casing.` I

also provide vent openings |29 between the space occurringat the'endof the casing between the housing or casing cover 5| and the stator end plate 46 communicatingwiththe annular open f space 06, which in turn is in communication with the low pressure portion of the casing.- 'I'he plate 51 is also provided with one or more lvents |3| to prevent building up pressure between the plate 51 and the inner end oi shaft 0|;

' Referring now to Fig. 18, the pipe 93 communi.- cates with onexside of the tank 9|, while the pipe 94 communicates with the opposite side thereof. Between the openings to the two pipes, I provide a plurality of screens |32 shown somewhat schematically. These screens may have any suitable shape and their function is to prevent any solid material from passing through the tank 9| into the pipe 0. It will be noted that a filler cap |33 on the same side of the tank as that with which the pipe\93 communicates. When it is necessary to supply additional oil to the system, it is done through the ller opening lcovered by thekcap |33, and any ioreign material which by any chance may be present in the oil is screened out. Preferably, the cap |33 is vented so as to `func' tion as an ordinary bleeder pipe toallowV air or gas 'or other vapor which may be present in the system tg pass into theatmosphere.

The tank 0| may be placed at any suitable position, but, as shown in Fig'. i8, I prefer to locate itin suchk away as to-utilize the cooling veiect of the usual-fan |34. 'If'hose skilled ,in the art will understand that the tank en may be provided with ns or any other type of device tqfacilitate removal'of yheat from the oil contained' therein, if necessary. Due to the construction of my transmission, however, the oil is normally maintained at 'a 'considerably lower temperature than in other types of hydraulic transmission devices lil ed in understanding the invention by a morecomplete description of the operation.

Assuming the transmission has been instailed and contains no oil, the first requirement in the operation is to fill all/,of the parts with oil or any suitable hydraulic iluid. The first step is to remove plugs |38 and |39 at the top of ,the casing and to see that plug |4| as well as pllg |26, at the bottom of the casinguare tight.',NoW set lever in high position to put variable pump at 0 capacity. Oil is now poured in through the opening |33 in the tank and, with both plugs |38 and |39 removed, air is permitted to escape through the top of the casing and oil will ow through both pipes 93 and 9d into the casing, all of the parts of which now are at atmospheric pressure. The'shaft 3| may be turned slowly until it begins to take hold" to facilitate admission of'oil to the hydraulic circuit including the two pumps. By this means, the entire casing may be lled with oil and enough oil admitted to the hydraulic circuit through the oil pressure chamber 82 and ports 8| to permit the pumps to operate hydraulically.

As soon as enough oil is admitted to cause a movement thereof ,through the hydraulic circuit,

operation of the transmission will automatically remove the additional air, assuming, of course, that sufficient oil is supplied to the tank 9| to replace it.. This is particularly brought about by allowing the transmission to free-wheel. The air at this time is passed to the tank 9| through the pipe 93 and oil returned through the pipe' 94 to take its place. It is understood, of course, that before the operation of the transmission is started, the plugs |38 and |39 are replaced.

At any time, but preferably after the transmission has been filled with oil so as to operate, the relief valve spring |22 is adjusted to the proper tension by the adjusting nut |23. -Those skilled in the art will understand how to make this adjustment. `In general it ymay be'stated, however, thatafter the proper setting of therelief valve for a particular size of transmission driven by aparticular size of power plant has been determined experimentally, the relief valve adjustments of a series of subsequently manufactured transmission units may all be the same. After an automobile has been driven with this predetermined setting, the relief valve may be further adjusted if the operating characteristics of the transmission disclose-that the maximum possible oil .pressure is either too high or too low.' The automobile engine is started in the usual. way with the shifting means at a neutral position. At this position, the capacity of the control pump at the right hand side of Fig. 1 yis the same as the capacity of the fixed capacity lpump at the left of Fig. 1. At this time, the ports in the control plate and stationary port housing are in positions indicated-schematically in Fig. 13.` As this figure shows, the intake ports `E58 in the control plate all due to their enlargement on the reverse side of the plate are in communication with the ports 53 which form part of the return circuit from the fixed capacity pump; and exhaust ports SS in the control plate 46 are in communication with the ports 6| forming part of the supply circuit to the fixed capacity pump.

At the same time, the intake and exhaust ports 'communicate with ports 19 in the stationary port housing, overlapping both edges of the ports 19,'

say approximately three degrees.

, With the ports disposedin this position andv the control plate set so .that the capacity of the variable capacity. pump is the same as the xed capacity pump,'all of the oil delivered from the.

variable capacity pump will be delivered to the xed capacity pump and returned .through the hydraulic circuit. At this time, the same condition exists, as explained schematically in Fig.

9, and not only does the shaft 33 fail to turn but.

theoretically it would be impossible to turn this shaft by the application of any force within the limits of the design. In thisembodiment, however, when both sides of the hydraulic circuit are in communication with each other through the ports 19, which are' also in communication' 4with the low pressure chamber 82, the output shaft can be turned. When set at neutral, therefore, the engine does not actas a brake and the automobile may be freely pushed or towed.

whether the engine is running or not.

The overlapping of the intake and exhaust ports with the ports 'l5 in neutral position serves another useful purpose. From a consideration of theequation,

it is evident that if there-were a. very slight dif-' ference between the capacity of the variable capacity pump and the capacity of the fixed capacity pump, there wouldbe a very high torque ratio approaching infinity between the shaft 3| and the shaft 33. Translated in terms of -operation of the transmission, this would mean that under lthese conditions .the automobile `would move either forwardly or .backwardly veryv slowlybut with tremendous power. This is an entirely undesirable situation, which is avoided by the arrangement of the ports in the manner shown in .the neutral position. Y

At a short distance on either side of neutral, equivalent for eXampleAto three degrees movement of the control plate 4 4, both sidesof the hydraulic circuit are kept in communication with' the low pressure chamber 82. This prevents building up pressure in.either side, which is necessary before the xedcapacity pump can operate to drive the shaft 33. This situation is not aifected by the position of the free-wheeling valve, because, even though this valve might be closed, theports 6| and 63 remain hydraulically coupled a short distance on either side of neutral. In the. further Iconsideration of the operation, it vwill be of some assistance to divide the hydraulic circuit between the two pumps, each of which comprises a pair of pump elements, into two parts, or separate circuits. The ports 6l and the ports in communication therewith constitute the oil supply connection from the variable cafl pacity pump to the xed capacity pump and may be termed the supply circuit. The ports 33 and ports in communication therewith receive the oil return from the xed capacity pump and deliver it to the variable capacity pump and may be termed the return circuit. Normally the now of oil is in the direction indicated by the terminology employed, but under some conditions the oil flow may be reversed. These terms are eused, therefore, for simplicity only and not in any limiting sense. When I speak of the two When it is desired to drive the automobile forwardly, the control plate is rotated through the operation of the rack 1i Y either manually or preferably automatically to decrease the capacity of the variable capacity pump. In this operation, the control plate moves in the direction in. dicated by the arrow in Fig. 2. Looking at Fig. 14, which represents the position of the ports in full forward position, the control plate 4t is moved in the direction of the arrow shown in this figure, it being understood, of course, that the rotor is rotatedin the direction indicated by the arrow adjacent the center point of the figure.

'Considering the full `forward position, it will be seen that the supply circuit (port 6|) is still in communication with the discharge port 69 and the return circuit (port 63) is still incommunication with the intake port 68 of the variable capacity pump. At this time also the port 19 is in communication with the discharge port 69. At this position of `plate 44 capacity of pump is zero and no iiuid is'entering or leaving the variable pump.

The discharge ofthe xed capacity pump per units vof time is determined by the difference in rotation of the shafts 3| and 33. At the direct forward. position, the variable capacity pump is.

pumping no oil and there 'is substantially no oil movement between the two pumps, and the shafts are caused' to move at substantially the same speed. However, at this time, when the engine is driving the car, a high pressure exists in thereturn circuit and a low pressure in the supply circuit. A study of Figs. 'I to 10, particularly a consideration of Fig. '1 will show that this condition rnust exist. Considering Fig. 14, it is clear that the return circuit (port 63) is shut off from the low pressure port 19, and a high pressure may be developed therein. The normal condition nf the supply circuit, however, is one of low pressure and so having .the supply circuit 6| in communication with the low pressure port andfthrough the valve 83 to atmosphere does not affect the operating .characteristics of the transmission in any way while the shaft 3i is driving the shaft 33. i

It'is through this connection, however, that-I obtain my free-wheeling characteristics. ils soon as there is a tendency for the shaft 83 to z overrun the shaft-3|, there is a tendency for the fixed capacity pimp to reverse its action and develop high pressure in the supply circuit.

" However, since the circuit is in communication which will permit the development of a pressure in the normally low pressure chamber 82 and, when this condition exists, the iluid cannot flow and the shaft 3l can drive the shaft Il and the motor may be used as a brake. l'Ihis'niay be vmade to occur as ankincident to the application of the foot brake as will appear/hereinafter.'

From a consideration of the principles' which' I employ, it is obvious that the control plate M may be set to any intermediate position between the positions shown in Fig. 14 and Fig. 13 which is the neutral position. In any intermediate;

position, thevshaft u will be driven inthe same direction that the shaft SIJisrotating, but at 'a slower speed. It isgclearthat as the control plate is shifted in the direction indicated!!!- thearrow in Figs. 2 leythevariable capacity pump gradually decreases in .capacity to zerdin position shown in Fig. 14. The relative speeds or torque ratio at any given setting of the control plate is determined by the equation previously considered. In other words, if the capacity of the variable capacity pump is half the capacity of the xed capacity pump, the torque and speed ratio between the shafts-will be ofthe order of .two to one. a l

The operation of the transmission to drive the automobile in -reverse isrnot4 dissimilar to the forward drive, except that the flow of uid in the circuit increases instead of decreasing. In reverse drive, however, the capacity of the variable capacity pump is greater-than the capacity of the xed capacity pump (see Fig. 10)'. In `full reverse drive (with the embodiment of the present invention in which the variable capacity pump has' a. maximum capacity approximately 25% greater than the capacity of thexxed capacity pump), the ports assume the relative position shown in Fig. 12. It will be seen that the return portion of the hydraulic circuit is in communication with the port 19 and, hence, in

communication with the low -pressure chamber '82, while the supply portion of the hydraulic circuit is in communicationonly with the exhaust port 89 of the variable capacity pump but not the variable lcapacity pump, it is evident that at l this, reverse p ion of this control plate, the maximum possible capacityfof the pump is attained. Aspreviously explained, thev control plate is prevented from moving to a position beyond that representing the maximum capacity by the stop surface. 18 (Fig. 2).

Whenthe transmission is set to cause a reverse drive of the shaft 33, the supply side becomes the high pressure side and the return side becomes the low pressure side. Looking at Fig. 12

again, itis apparent that 'the' return circuit 63 or normally low pressure" side in reverse is connected to atmosphere through the ports 1Q with the result that free-wheeling is accomplished iny reverse the same as in forward drive whenthe valve 83 is opened. Similarly, free-wheeling canbe cutout in reverse drive by closing this valve.

It follows as in forward position that any posi? tion of the control plate intermediate positions shownin Figs. .13 and 12 .will cause a reverse drive with the single exception, of course, .that- I no driving action takes place within the neutral zone or until the ports 68 are taken. outi of communication with the ports 18.' l

. For convenience in following the hydraulic ilow, the ports in Figs. 12 to 14 are provided with a series of arrows which represent the prevailing movement .of the huid. I also show a hydraulic diagram in Fig. 15l but before considering this considered.

diagram further details of the' operation will be 'I'he entire transmission is designed to be com, a

' pletely filled with oil at all times; and due to the construction employed, there will be very little tendency for the leakage of -oil from the hydraulic system. However, there will be some slight* escape of oil and-,'when the automobile cape of oil through' the free-wheel valves'. The high pressure side f the circuit will tend, at all times, to remain filled with oil by reason of the action of the pumps alone and any shortage of oil will tend to manifest itself by the creation of a sub-atmospheric pressure inthe low pressure side of the circuit, which is in communication with the fluid filled casing through either one of check valves 86 and 81. .At any time when pressure in either the supply or return circuit is less than the pressure in the outer 4casing, one of the valves will be unseated and admit oil until the pressure is substantially equalized. The check valve action of these two valves, however, will at all times prevent high .pressure iiuid in the system from discharging into the outer casing.

The oil pressure on the inside edges of the vanes is maintained the same as the maximum oil pressure in either side of the system. Due to the actionof the valve IM, the oil chambers 43 and 53 adjacent the vanes in both pumps is alwaysin hydraulic communication through the passages 98, |08, 101, lll, |09 and H2 with the high pressure side of the system. The series .of ports and openings communicating with the vanes is really then a party of the hydraulic system connected into the high pressure side thereof and may be termed the vane system.

I have already described the action of the relief valve IZI. It is clear that particularly at high torque ratios, it is possible to `develop an enormous pressure in the high pressure side of thesystem and, if the output shaft 33 for any cause whatsoever resists movement, serious breakage might occur. All of the parts of the transmission and all of the drive parts of an automobile, for that matter, are constructed with an ample factor of safety, but, due to the fact that torque ratios higher than usual are -possible with my transmission, it would be pracit is true, tends to generate heat and is undesirable for this reason. Since it is meant as a safety precaution entirely, however, and possibly may never operate in normal operation of an automobile, its presence in the transmission may be of considerable value.

The neutral zone in itself acts as a safety fea-v ture in addition to acting to prevent creeping. Without this neutral zone substantially infinite gear ratios would be possible, which might result in breakage should the output shaft resist movement.

Now, considering the hydraulic circuit in Fig. 15 it is seen that the variable capacity pump cir- Y cuit indicated schematically at the right, is set to ,what is usually termed direct/ forward drive,

A movement of oil through the supply and return circuits indicated by the words supply and return. I show arrows indicating the normal direction of flow, however, at speeds in which theV torque ratio is greater than one to one. It will be understood, therefore, that throughout the hydraulic diagram, the arrows generally indicate thev direction of flow but are not .to be taken literally under al1 conditions.

vIn the hydraulic circuit, I indicate schematically the position of the free-wheeling valves 83 and 85, the safety valve I2 I, and two check valves 86 and 81 for admitting fluid from the casing 23 to the hydraulic circuit, and the control piston valve lill! in its chamber 98. The vane system, also indicated schematically, is marked vane" for identification. l

Fig. 11 is a mathematical representation of the operation of my transmission based upon the displacement per revolution of the two pumps. The curve represents the equation plotted with the resulting torque R as ordinates and. displacement of variable capacity pump a as absissas. The displacement of the variable capacity pump indiatedby the character a, in Figs. 7 to 9, is in terms 'of the displacement A, of the xed capacity pump and the resulting torque R of the output shaft is in terms of the torque P imposed on the input shaft. By a study' of Fig. 11, it is clear that with a displacement of a equal to live-fourths of A, the value of R at the left of the chart:v 4P which indicates that a reverse torque of four to one is obtained, and inversely,

the output shaft will rotate at one-fourth the speed of the input shaft but in a negative direction. The shaded portion on both sides of the two axes represents the neutral zone in which'no driving movement takes place on account of the junction of the supply and return circuits through portv 19 (Fig. 13) From a study of the curve Where the value of a is less than A, it is clear .that I can obtain a complete range of forward torque' ratios from approximately 8 P to P, where P represents the torque of the input shaft. In other words, I have a complete range of torque ratios from a torque ratio of approximately eight to one to a. torque ratio of one to one with a corresponding inverse range of speed ratios.

The description of the operation is based upon a control of the control plate M'wherein the capacity of the variable capacity pump ranges from zero to a capacity of approximately 25% more than the capacity of the fixed capacity pump. Froma st udy of Fig. 2, however, it is clearv that the control plate M may be shifted further to a position representing reversal of the intake and exhaust ports of the variable capacity pump. In effect, this causes the pump to work backwards andthe exhaust port becomes the intake and. the intake the exhaust. When the ports in the variable capacity pumpy are reversed, they may again be positioned to varythe capacity.` of the variable capacity pump in a reverse direction. When these ports are reversed, the movement of the oil in the hydraulic circuit will also'be reversed and will' flow through the hydraulic circuit 63 heretofore referred to as the return circuit, then through the xed capacity pump, then to the portion of the circuit v6I heretofore referred to as the supply circuit and back to thevariable capacity pump. The result of this reverse flow is an overdrive of the shaft 33. Those skilled in the art of mathematics will understand how to continue the chart in Fig. 11 for negative values of a when my trans- 2,001,325 mission is set for overdrive. Further description of the overdrive, therefore, need not be given.

My invention lends itself to the provision of automatic transmission operation for decreasing the torque ratio as the speed of the automobile is increased. It is clear that any suitable means operated automatically` in response to the speed of the automobile, may be made leffective to shift thecontrol rack 1|. In Fig. 19, I show one em `bodiment of a suitable .control mechanism housing forms the end plate 5| of the transmission casing. The output shaft 33 may be considered as th'e propeller shaft running to the usual dierential (not shown) for driving the rear wheels. vMy preferredjmeans of controlling the transmission automatically is voperated in' resporise to the speed of the output shaft. It will be understood that the shaft indicated as 33 in Fig.

19 maybe merely an extension of the output shaft shown in Fig. 1, for example, but coupled thereto, or any other element revolving in coordination with shaft 33. For the purpose of the present explanation, however, it may be assumed thatthe shaft 33 in Fig. 19 is the output shaft.

' The output shaft is provided with a housing |46 at an enlarged'portion of Awhich a control arm |41 is pivoted as at |48. The lower end of the controlarm rides in an annular groove |49 in a control block |5| feathered on the shaft 33. Adjacent the' slidable control block |5|, I mount a bracket |52 carrying centrifugally operated devices l53. These devices are in the form of bell cranks pivoted to the bracketi52. one of the arms thereof engaging against the block 5| and Vthe other arms provided with weights |54. Itis clear that rotation of the shaftl 33 tends to move the force thereby forcing the block |5| in a left hand i t d rection and actuating the control arm abou its double beu crank arm 5g f pivot |48.

In order to return the control arm |41 to theY at rest position, I provide a spring |56, having one end secured to the upper part of the control arm and the other end secured to a cable |51.-

'Ihis cable is brought up to a suitable tension ,control mechanism |58 placed on the dash so that by adjusting the position of the tension control mechanism the tension of the spring |56 can be modified. Since the centrifugal devices must operate against the force of the spring |56, it is clear that thetension in this spring will determine the force which the centrifugal devices must exert `before imparting movement to the control arm |41. The centrifugal force is determined by the speed of the output shaft 33 so that it is clear that by adjusting the tension control device |58, the speed at which the automobile .is travelling when direct transmission occurs may be predetermined.

By utilizing the movement of the control arm |41, the control rack 1| may be adjusted to change the drive ratio between the input and output shafts. For shifting between reverse and forward drive, I 'employ a construction utilizing in a general way the principle of the Stevenson link. A double bell crank lever |59 is pivoted at |6| to the transmission casing and has an arm slid- Y 1 i 1 L .ably pivoted at |62 to the top. ofthe control rack 1|. The double bell crank lever is provided with a substantially vertical slot |63 in which a-srnall block |64 is adapted to slide. In the position shown in the drawings, theblock |64 is at the top of the slot.

verse drive position as will be shown.

This is the forward drive positionA and means is provided for shifting to the re- Normally the double bell crank lever |59 is in a position to holdv the rack 1| in the neutral position. I provide means, however, to initiate movement of the shaft 33, this means being ioperated preferably as an incident to the speeding up of the engine. The/usual foot throttle |66 projecting through the -oor boards has its lower end connected to a lever |11 pivoted at |18. This lever has an arm |19 pivoted to a carburetor control rod I8 the movement of which, in a suitable.

manner understood in the art, 4will increase the (a roller as'shownmay be employed) has a cam surface |83a so shaped that` when the foot throttle is pressed downwardly the bell crank lever |83 moves on its pivot in a counter-,clockwise direction and through the. link |86'rnoves the double bell crank lever |59 past the neutral position. This will;be a position in whichl the port 68 (Fig. 13) is moved in a counter-clockwise direction out of register with the port 19. operation previously described, starts 'the Aoutput shaft 33 rotating at or above approximately.one-. eighth the speed of the input shaft.

This, through the f As soon as the shaft 3 3 starts to rotate,.thev

centrifugal devices carried. by it begin to operate tion. The' control arm |41 is connected by'asuitable link |81 to the block |64. Accordingly, movement ofthe control arm, as the shaft begins to turn, causes a still greater movement of the The shaft 33 gradually increases -in speed due in part to the' fact that the engine may be gradually driving faster and also due to the automatic shifting of the rack 1|l thereby decreasing the torque ratio between the input and output shafts.. In this way, the output shaft is gradually 4o andgradually force the control block 15| against the action of the spring |56 ina left handdirecbrought upto the speed of the input shaft, thel length of time required being determined by tension on the spring |56, the less the tension, the shorter the length of time.

speed of theshaft 33 will gradually increase as the momentum of the automobile increases until finally the shaft 33, at relatively high automobile speed, will be rotating faster than the vshaft 3|.

For reverse drive, I provide a foot pedal |88 y near the accelerator pedal |66 in the form of a rod, the lower end of which is pivoted to one arm of a lever |89, another-arm of which has secured thereto a link |91 which, through suitable connections'such as shown, including a vertical link |82, double arm levers |93 and |94 and a connecting link |96, is adapted to pull the block |64 to the opposite end of the slot |63. Movement of the double bell crank lever |59 thereafter, either through the link |86 or the link |81, will move the double bell crank in a counterclcckwise direction thereby depressing the rack 1| and car- "f When the trans-l mission is constructed to permit overdrive, the' g secured by reversing these connections.

rying it to the reverse positionsin which the ports will be moved to the position shown in Fig. 12. It will be understood that the foot pedal |88- and -the foot throttle |66 are so positioned that they can be operated by the same foot.

As shown in Fig. 19, the free-wheeling valve 83 is operated by the brake pedal |91. "Ihe brake pedal is shown pivoted on a pin |98 carried by the casing 32 and secured to a brake rod l99 which, in a suitable way, operates a suitable type of wheel brake. A short free-wheeling control leverl 20! isprovided and suitably connected to the control valve 83 and this lever, through a link connection 202, is moved as an incident to the operation of the `brake pedal. With this ar' rangement, the transmission may be set for freewheeling at all times when the foot brake is not applied. However, when the foot brake is applied to bring the automobile to rest, the valve 83 is closed and the engine operates as a brake, and therefore, during deceleration, the shaft 33 slows down, the weights |54 are forced inward by the spring l|56 and, as the automobile is coming to rest, the bell crank |58 is operated to bring the control plate 44 to the neutral position, through all the intermediate torque ratios and correspondingly multiplies the braking effect of the engine.

It will be understood that either the free-wheeling valve 83 or 85 may be used alone, or I may provide no free-wheeling control valve, in which case the transmission could be constructed to freewheel at all times or, on the other hand, could be constructed so that it would never free-wheel. From this consideration, it is clear that the freewheeling control is merely a valuable adjunct, but some of the most important features of my invention may be utilized either with or without free-wheeling.

The free-wheeling control valve 85 is shown operated by a handle 80 which could, for example,

project up vvthroughthe floor boards. "Ihose skilled in the art will understand that this is merely illustrative, however, as the control for this valve maybe placed in any suitable position utilizing well known mechanical remote control devices.

The invention has been described throughout with the rotor of the fixed capacity pump secured to the input shaft and the stator of this pump secured to the output shaft. It is obvious, however, that'substantially the same results can be It is the relative movement between the stator and rotor of the fixed capacity pump which is important and the two pump elements thereof are inter-1 changeably connected to the output and input shafts.

lfact a stator but rotates aty the same speed as the rotor. Wherever these terms are employed, it ls obvious that they are employed in thel sense of pump elements except where the context indicates a specific or literal meaning. 'I'he pumps are describedl as rotary vane pumps. pumps, however, `may be employed without departing from the spirit of the invention.

Although I have described my invention in detail to permit -thoseskilled in the art to practice it, it is'obvious that I am not restricted to the specic form shown and the invention is limited only by the scope of the appended claims.

What I claim as new and desire to protect by Letters Patent of the United States is:

Other forms of 1. In a hydraulicttransmission, a power input shaft, a vpower output shaft, a rotary variable capacity pump having a stationary stator and a.

rotor secured. to and driven by said input shaft,

pump, -said fixed capacity pump having a rotorA fixed capacity pump to the intake of the variable capacity pump, and a casing surrounding saidpumps adapted to contain oil under substantially atmospheric pressure, a cooling and separating tank,'and means utilizing the stator of the xed capacity pump as a separate impeller for discharging oil from the casing and delivering the same to the cooling and separating tank, and gravitymeans for delivering 'oil from said tank back to the casing.

2. In aA hydraulic transmission, a power input shaft, a power output shaft, a rotary variable capacity pump having a stationary stator and a rotor secured to and driven by said input shaft, a fixed capacity pump having less capacity than the maximum capacity of the variable capacity pump,'said fixed capacitypump having a rotor driven by said input shaft and a stator connected to the output shaft. whereby the capacity of said xed capacity pump per unit oftime is determined by the diifer- Y ence in rotation of thetwo shafts, ported means forming a connection from the discharge side ofv drive, and means for venting both interconnect.- f

ing ports between the pumps at positionsat both sides of neutral wherebycreeping is avoided.

3. In a hydraulic transmission, a power input shaft, a power output shaft, a rotary variable capacity pump having a stationary stator and a rotor secured to and driven by said input shaft, a xed capacity pump having less capacity than the maximum capacity of the variable capacity pump, said fixed capacity pump having a r tor driven by said input shaft and a stator connec ed to the output shaft whereby the capacity of said fixed capacity pump per unit of time is determined by the difference in rotation of the two shafts, ported means forming a connection from' the discharge side 'of the variable capacity pump to the intake of the xed capacity pumima connection from the discharge of the fixed capacity pumpto the intake of the variable capacity pump, means controlled by the speed of the output shaft .for varying the capacity of the variable capacity pump vfrom zero capacity to capacity vequal to the capacity of the `fixed capacity pump whereby trolled within ratios representing neutral and direct drive, means to reverse the action of said speed controlling-means whereby the rotation and torque ratio of the output shaft will be reversed,

the torque ratio of the output shaft may be conpump from zero capacity to capacity equal to the and means for venting both interconnecting ports between the pumps at positions at both sides of neutral whereby creeping is avoided, said reverse fixed capacity pump per revolution of the inputshaft is controlled by the difference in rotation of the two shafts, ported means having a connection from the discharge side of the variable capacity pump and the intake of the fixed capacity pump, and a connection for connecting the vdischarge from the fixed-.capacity pump to the intake of the variable capacity pump, and means controlled by the speed ot the output shaft for varying the capacity of the variable capacity capacity of the fixed capacity pump whereby the torque ratio of the output shaft may be controlled within ratios representing neutral and direct drive and means to reverse the action of said speed controlling mea'ns whereby the rotation and torque ratio of the output shaft will be reversed,

said reverse means including means for controlling the capacity'of the variable capacity pump between its maximum capacity and the capacity o'f the fixed capacity pump.

5. In a hydraulic transmission, a power input shaft, a power output shaft, a rotary variable capacity pump having a stationary stator and a rotor secured to and driven by said input shaft,

a fixed capacity punp having less capacity than the maximum capacity of the variable capacity pump, said fixed capacity pump having a rotor driven by said input shaft and a stator connected to the output shaft whereby the capacity of said fixed capacity pump per unit of time is determined by the difference in rotation of the two shafts, ported means forming'a connection from the discharge side of the variable capacity pump to the intake of the fixed capacity pump, a connection from the discharge of the fixed capacity pump to the intake of the variable capacity pump, means for varying the capacity ofthe variable capacity pump 'from zero capacity to`capacity greater than the capacity of the fixed capacity pump whereby the torque ratio of the output shaft may be controlled within ratios representing neutral, direct drive, and reverse drive, and

means for venting both interconnecting ports between the pumps at positions at both sides of neutral whereby creeping is avoided, saidcapacity varying means being operable to reverse the variable capacity pump to provide overdrive.

6. In a hydraulic transmission, a power input shaft, a power output shaft, a rotaryvariable capacity pump having a stationary stator and a rotor secured to and driven byssaid input shaft, a fixed capacity pump having less capacity than the maximum capacity of the variable capacity pump, said fixed capacity pump having a rotor' driven by said input shaft and a stator connected to the output shaft whereby the capacity of said xed capacity pump per revolution of the input shaft is determined by the difference in rotation of the two shafts, and ported means forming a connection from the discharge side of the variable capacity pump to the intake of the fixed capacity pump, a connection from the discharge of the fixed capacity pump to the intake of the variable capacity pumppand means controlled by the speed of the output shaft for varying the capacity of the variable capacity pump to modify the torque ratio between the shafts in forward and reverse, whereby either connection in the ported means may contain oil under-pressure, and means for limiting the pressure in said ported means.

.7. In a hydraulic transmission, a power input shaft, a power output shaft, a rotary pump having a stationary stator and a rotor secured tp and driven by said input shaft, a second rotary pump of less capacity than said first mentioned pump, said second pump having a rotor driven by said input shaft and a stator yconnected to the output shaft, whereby the capacity of said second pump per revolution ofthe input shaft is determined by the difference in rotation of the ktwo shafts, a ported lcontrol plate associated with said 'first mentioned pump, means controlled by the speed of vthe output shaft for adjusting said control-plate to vary the capacity of said pump, ported means forming connections to thel intake and discharge sides of said second pump, means carried by said control plate for interconnecting said connections with the intake and discharge sides of said first mentioned pump, a\low pressure chamber, .and means associated with said control plate for opening either or both of said connections .to said low pressure chamber. y

8. In a hydraulic transmission, a power input shaft, a power output shaft, a rotary pump having a stationary -stator and a' rotor secured to and driven by said input shaft, asecond rotary pump of l less capacity than said rst mentioned pump, said second pump having a rotor driven by said input shaft and a stator connected to the output shaft, whereby the capacity of said second pump per revolutionof the input shaft is determined b'y the difference in rotation ofthe two shafts, a ported control plate associated with said first mentioned pump, means for adjusting said control plate to vary the capacity of said pump, ported means forming connections tothe intake and dischargesides ofsaid second pump, means carried by said control plate for interconnecting said connections with the-intake and discharge sides of said first mentioned pump, a low pressure chamber, and means associated with said control plate for opening either or both of said connections to said low pressure chamber.

9. In a hydraulic transmission, a power inputs*V shaft, a power output shaft, a rotary pump having,

ported means forming connections to the intake and discharge sides of said second pump, lmeans carried by said control plate for interconnecting said connections with the intake and discharge sides of said first mentioned pump, a low pressure chamber, and means associated` with said control plate for opening either or bothof said connections to said low pressure chamber.

10. In a hydraulic transmission, a power input shaft, a power output shaft, a rotary pump having a fixed stator and having a rotor driven by the input shaft, a second pump having a stator secured to the power output shaft and a rotor driven by the power input shaft, a ported control plate associated with the rst mentioned pump, means controlled by the speed of the output shaft for adjusting said ported control plate to vary the capacity of said pump, a stationary port housing having a plurality of ports, means associated with the control plate for connecting said ports to the intake and exhaust ports of the rst mentioned pump, a rotatable port housing secured to the stator ofthe second mentioned pump and having ports connected tothe intake and exhaust ports of said second mentioned pump, and means for interconnecting the ports inthe stationary port housing and the rotatable port housing to provideva closed hydraulic circuit between the 11. In a hydraulic transmission, a powerinput shaft, a power output shaft, a rotary pump haviing a xed stator and having a rotor driven by the input shaft, a second pump having a stator secured to the power output shaft and a rotor f driven" by the power input shaft, a ported control plate associated with the rst mentioned pump, means for adjusting said ported 'control' plate to vary the capacity of said pump, a stationary port housing having a plurality of ports, means associated withlthe control plate for connecting said ports to the intake and exhaust ports of the rst mentioned pump, a rotatable port,

housing secured to the stator of the second mentioned pump and having ports connected to the intake and exhaust ports of said second mentioned pump, and means for'interconnecting the ports in the stationary port housing and the rotatable port housing to provide a closed hydraulic circuit between the pumps.

12. In a hydraulic transmission, a power input shaft, a power'output shaft, a rotary pumphaving a fixed-stator and having a rotor driven by the input shaft, a second pump having a stator secured to the power output shaft and a rotor driven by the power input shaft, a ported control plate associated with the first mentioned pump, means for adjusting said ported control plate to vary the capacity of said pump, a stationary port housing having a plurality of ports, means associated with the control plate for connecting said ports to the intake and exhaust ports of the first mentioned .'pump, a rotatable port housing secured to the stator of the second mentioned pump and having ports connected to the intake and exhaust ports of said second mentioned pump, means for linterconnecting the ports in the stationary port housing and the rotatable port housing to provide a closed hydraulic circuit between the pumps, a

low pressure chamber, a port in the stationary for adjusting said. ported control plate to vary the capacity of said pump, a stationary port housing having a plurality of ports, means associated with the control plate for connecting said ports to the intake and exhaust ports of the first mentioned pump, a rotatable port housing se'curedto the stator of the second mentioned pump .and

having ports connected to the intake and exhaust Y Y movement of the control plate to connect tosaid lowpressure port the lowfpressure side of said hydraulic circuit whereby a uni-directional'driving effect-is obtained between the input vandoutput shafts. l

14. The combination defined'in claim 13, in-

cluding means for closing off said 4low pressure`l chamber to provide a bi-direcitional drive connection between said shafts. 15. The combination defined in claim l?, including means for hydraulically interconnecting said supply circuit and return circuit whereby the pressure is substantially eqalized throughout the closed hydraulic circuit.

116. The combination defined in claim 13, wherein said first mentioned pump has a greater ca- I pacity than the second mentioned pump, the output shaft being stationary when the control plate isset, to equalize the capacities of the pump.

17 The combination denedin claim 13 wherein said flrst mentioned pump has a greater ca- -pacity than the second mentioned pump, the out put shaft being stationary when the control plate is set to equalize the capacities of the pumps, such setting of the control plate comprising alneutral position, and means for interconnecting the supply circuit and return circuit when the control plate associated with the first mentioned pump,

means for adjusting saidported control plate to vary the capacity of said pump, a stationary port housing having a plurality'of ports, means associated with the control plate for connecting said ports to the intake and exhaust ports of the first mentioned pump, a rotatable-port housing secured to the stator of the second mentioned pump and having ports connected to the intake and exhaust ports of said. second mentioned pump, means for interconnecting the ports in the stationary port housing and the rotatable port housing to'providea closed hydraulic circuit between the pumps including a supply circuit and a return.r

circuit, eitherv said supply circuit or return circuit adapted to contain oil under relatively high pressure, as determined by the adjustment of said control plate, and means for limiting said pressure. i

19. The combination ,defined in claim 18, where 

